D-Link DIR-456U Hardware Revision A1 (End-of-Life, EOL) contains a hardcoded telnet backdoor. The device starts a telnet daemon at boot via /etc/init0.d/S80telnetd.sh with the username "Alphanetworks" and the static password "whdrv01_dlob_dir456U" read from /etc/config/image_sign. The custom telnetd binary accepts a -u user:password flag, and the custom login binary uses strcmp() to validate credentials. Successful authentication grants an unauthenticated attacker on the local network a root shell with full administrative control. The device has reached End-of-Life (EOL) and will not receive patches.
References
| Link | Resource |
|---|---|
| https://www.securin.io/zero-day/cve-2026-42376-hardcoded-telnet-backdoor-in-d-link-dir-456u-a1-end-of-life- | Exploit Third Party Advisory |
| https://www.securin.io/zero-day/cve-2026-42376-hardcoded-telnet-backdoor-in-d-link-dir-456u-a1-end-of-life- | Exploit Third Party Advisory |
Configurations
Configuration 1 (hide)
| AND |
|
History
11 May 2026, 19:39
| Type | Values Removed | Values Added |
|---|---|---|
| First Time |
Dlink
Dlink dir-456u Firmware Dlink dir-456u |
|
| CPE | cpe:2.3:o:dlink:dir-456u_firmware:-:*:*:*:*:*:*:* cpe:2.3:h:dlink:dir-456u:a1:*:*:*:*:*:*:* |
|
| References | () https://www.securin.io/zero-day/cve-2026-42376-hardcoded-telnet-backdoor-in-d-link-dir-456u-a1-end-of-life- - Exploit, Third Party Advisory |
04 May 2026, 17:16
| Type | Values Removed | Values Added |
|---|---|---|
| New CVE |
Information
Published : 2026-05-04 17:16
Updated : 2026-05-11 19:39
NVD link : CVE-2026-42376
Mitre link : CVE-2026-42376
CVE.ORG link : CVE-2026-42376
JSON object : View
Products Affected
dlink
- dir-456u_firmware
- dir-456u
CWE
CWE-798
Use of Hard-coded Credentials